Short wave arrangement



March 31,-1942.- w. BUSCHBECKQ 2,273,238

SHORT WAVE ARRANGEMENT Filed Oct. 12', 1 940 lNVE NTOR.

ATTORNEY ?atented Mar. 32, E942 I a ain snoa'r wart: ARRANGEMENT Werner Buschbeck, Berlin, Germany, assignor to 'ilelefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation ct Germany Application ember 12, mesa-a1 No. 360,900 in Germany July 21, 1939 5 iaims. i. 170-111) hollow tube forming a coil, the coil acting as the inductance of a tank circuit and the conductor acting to carry direct current from' the low radio frequency potential point up tothe high radio frequency potential end without the direct current voltage being applied to the coil. Where short waves are concerned, and where slider contact variometers are used, however, it may happen that the concentric line formed by the inner conductor and the inside of the outerconductor assumes a state of resonance in respect to the working wave or-a harmonic thereof, and this is liable to lead to inadmissible high radio frequency potentials between said conductors which may cause destruction of the insulation therebetween.

According to the invention, this concentric line,

though not intended to carry any radio frequency energy, at its radio frequency ground end is terminated by an ohmic resistance shunted for direct current and corresponding to its character istic impedance. This resistance (because of the rubber or paper insulation of the cable) is always of a low resistance value, and the radio frequency resistance. measured between conductors of this line at its other end is, of course, the

-same. Hence, no large voltage can exist between inner and outer conductors.

The appended drawing illustrates an exemplified embodiment of this idea employing an amplifier tube for amplifying the fundamental frequency. The plate choke-coil D is no longer called upon to choke the whole plate alternating potential, but merely the same fraction thereof which is given by the drop of potential across the plate blocking condenser B. This voltage, as was explained above, is relatively small, so that the impedance of choke D needs only be pedance of the concentric line, and even in the case of very short waves a choke meeting this requirement is readily constructed so that it will not show undesirable resonance characteristics.

large compared with the low characteristic im-' Elements S and B are radio frequency by-pass condensers.

Of course, care must be taken so that, inside the wave band dealt with, the capacitive reactance of the plate shorting condenser S is small, or the inductive reactance of the choke-coil U shunting the terminating resistance R is high, compared with the surge or characteristic impedance of the concentric line composed of the inner and outer conductors, and this is readily feasible in the majority of cases. Resistance R is a dissipative resistance which dissipates standing waves inside'the coil, and thereby assuresthat no large voltage arises between any adjacent parts of the concentric line.

What is claimed is: 1. In a radio frequency electron discharge de vice having a coil connected at one end to ground and at the other end to the anode for radio frequency energy, means for feeding direct current to said anode comprising a second coil closely coupled to said first coil, and means for preventing standing waves from occurring between said two coils comprising a dissipative resistance connected between a point on one of said coils and an adjacent point on anotherof said coils.

2. An electron discharge device in accordance with claim 1, characterized in thisthat said first coil is hollow and said second coil is located in the interior of said first coil.

3. A short wave amplifier for amplifying without change of frequency, comprising an electron discharge device having an anode, a cathode and a grid, a coaxial line in the form of a coil, a capacitive connection of low impedance to energy of the operating frequency coupling said anode to one end of the outer conductor of said line, a choke coil connecting said anode to the adjacent end of the inner conductor of said line, a connection from the other end of said outer conductor to said cathode, and a terminating resistor connecting the other end of said inner conductor to the cathode through a capacity of low impedance to energy of the operating frequency.

4. A short wave amplifier for amplifying without change of frequency, comprising an electron discharge device having an anode, a cathode and a grid, a coaxial line in the form of a coil, a capacitive connection of low impedance to energy of the operating frequency coupling said anode to one end of the outer conductor of said line, a choke coil connecting said anode to the adjacent end of the inner conductor of said line, a connection from the other end of said outer conductor to said cathode, a terminating resistor connecting the other end of said inner conductor to the cathode throughra capacity of low impedance to energy of the operating frequency, a connection from the positive terminal of a source of direct current potential to that end of said resistor which is removed from said inner conductor for providing a polarizing potential for said anode, and a choke coil shunting said resistor. 7

5. A short wave amplifier for amplifying without change of frequency, comprising an electron discharge device having an anode, a cathode and a grid, an oscillation circuit tuned to the operatof said inner conductor to the cathode through a capacity of low impedance to energy of the op. erating frequency. I

WERNER BUSCHBECK. 

